Buggy code:
public final class ValidationFilter extends AbstractXMLFilter { private final MessageUtils messageUtils = MessageUtils . getInstance ( ) ; private final Set < String > topicIds = new HashSet < String > ( ) ; private Map < String , Map < String , Set < String > > > validateMap = null ; private Locator locator ; private final Deque < String [ ] [ ] > domains = new LinkedList < String [ ] [ ] > ( ) ; private URI currentFile ; private Job job ; private int cols ; private int columnNumber ; private Locator colsLocator ; private Mode processingMode ; public ValidationFilter ( ) { } public void setValidateMap ( final Map < String , Map < String , Set < String > > > validateMap ) { } public void setCurrentFile ( final URI currentFile ) { } public void setJob ( final Job job ) { } public void setProcessingMode ( final Mode processingMode ) { } @ Override public void setDocumentLocator ( final Locator locator ) { } @ Override public void startElement ( final String uri , final String localName , final String qName , final Attributes atts ) throws SAXException { } @ Override public void endElement ( final String uri , final String localName , final String qName ) throws SAXException { } private void validateCols ( final Attributes atts ) throws SAXException { if ( TOPIC_TGROUP . matches ( atts ) ) { <START_BUG> colsLocator = new LocatorImpl ( locator ) ; <END_BUG> final String c = atts . getValue ( ATTRIBUTE_NAME_COLS ) ; try { cols = Integer . parseInt ( c . trim ( ) ) ; } catch ( final NumberFormatException e ) { if ( ( processingMode ) == ( Mode . STRICT ) ) { throw new SAXException ( messageUtils . getMessage ( "DOTJ062E" , ATTRIBUTE_NAME_COLS , c ) . setLocation ( locator ) . toString ( ) ) ; } else { logger . error ( messageUtils . getMessage ( "DOTJ062E" , ATTRIBUTE_NAME_COLS , c ) . setLocation ( locator ) . toString ( ) ) ; } cols = - 1 ; } } else if ( TOPIC_COLSPEC . matches ( atts ) ) { ( columnNumber ) ++ ; } else if ( ( TOPIC_THEAD . matches ( atts ) ) || ( TOPIC_TBODY . matches ( atts ) ) ) { if ( ( ( cols ) != ( - 1 ) ) && ( ( columnNumber ) > ( cols ) ) ) { if ( ( processingMode ) == ( Mode . STRICT ) ) { throw new SAXException ( messageUtils . getMessage ( "DOTJ063E" , Integer . toString ( cols ) , Integer . toString ( columnNumber ) ) . setLocation ( colsLocator ) . toString ( ) ) ; } else { logger . error ( messageUtils . getMessage ( "DOTJ063E" , Integer . toString ( cols ) , Integer . toString ( columnNumber ) ) . setLocation ( colsLocator ) . toString ( ) ) ; } } columnNumber = 0 ; } } private AttributesImpl validateLang ( final Attributes atts , final AttributesImpl modified ) throws SAXException { } private void validateId ( final Attributes atts ) throws SAXException { } private AttributesImpl validateHref ( final Attributes atts , final AttributesImpl modified ) { } private void validateAttributeValues ( final String qName , final Attributes atts ) { } private void validateKeys ( final Attributes atts ) { } private void validateKeyscope ( final Attributes atts ) { } private boolean isValidKeyName ( final String key ) { } private void validateAttributeGeneralization ( final Attributes atts ) { } private AttributesImpl processFormatDitamap ( final Attributes atts , final AttributesImpl modified ) { } }

Fix:
colsLocator = ( ( locator ) != null ) ? new LocatorImpl ( locator ) : null ;